The present invention relates to fuel storage vaults and, in particular, to a ventilated, below-grade, containment vault that contains one or more primary, liquid storage tanks. A manhole permits access to the vault and spill and overflow containment assemblies direct spillage and vent overflow to the primary, secondary or tertiary storage spaces. Dispensing pumps are secured to a top wall containing sundry conduits, accessory fixtures and support equipment.
A byproduct of society's increasing awareness to the environment and growing concerns toward ground water contamination and the adverse effects of spilled petrochemicals (e.g. oil, gasoline etc.) has been the institution of varieties of regulatory controls over related storage vessels. The controls are intended to promote safe fuel storage and contain spills. A primary goal is to avoid contaminated soils, such as commonly found at the sites of gasoline stations, fueling depots and other fuel handling sites. The contamination can insidiously occur over time from small leaks or from a single large spill.
The fuel delivery industry has a separate desire for automatic, attendant free dispensing stations. The station should be compatible with all regulatory requirements and permit fuel delivery with either cash or credit card. Appurtenant storage tanks may either mount above or below grade and controls should be available to make the tanks substantially self-sufficient.
A variety of below-grade storage containers have been developed for containing pressurized and non-pressurized, flammable liquids, such as gasoline, propane or natural gas. Some of these containment vessels and tanks are shown at U.S. Pat. Nos. 1,958,487; 3,151,416; 3,995,472; 4,183,221; 4,607,522; and 4,653,312. The foregoing containers generally provide assemblies that include a primary, metal containment chamber that is surrounded by a reinforcing material, such as concrete. Various arrangements of intervening layers of insulators and/or liquid impermeable materials are also included in the various tank assemblies.
Numerous above-grade storage vessels are also known. Most of these vessels provide only a tank assembly having a single skin or single layer of material, such as metal or concrete. Rupture or damage to the tank wall most typically results in an uncontrolled and unconfined spill. To avoid unconfined spills, some tanks are mounted behind a surrounding berm wall or dike.
In lieu of a dike, some tanks are constructed with a multi-layered construction that includes a primary tank surrounded by a concrete or metal structure. The primary tank may be integrated into the surrounding structure. U.S. Pat. Nos. 2,083,491; 2,136,390; 2,777,295; and 4,513,550 disclose cast concrete containment chambers wherein the structural walls include liquid impermeable liners.
Still other above-grade storage vessels are disclosed at U.S. Pat. Nos. 2,544,828; 3,562,977; 4,366,654; 4,372,906; 4,552,166; 4,826,644; 4,911,326; 4,934,122; and 4,986,436. Some of the foregoing storage tanks provide a primary, metal containment chamber that is surrounded by a monolithic cast concrete vault. One or more intervening membranes, impermeable to a contained liquid, are also provided to obtain secondary containment.
Another metal storage vessel having secondary containment is shown at U.S. Pat. No. 4,895,272. Also included in this tank is an assembly for directing spillage from the vent into a secondary storage space. U.S. Pat. No. 5,769,109 discloses a spill containment collar to direct spillage into the primary tank and/or a secondary storage space. Other above-grade, metal storage tanks of double wall construction or having spill containment capabilities are shown at U.S. Pat. Nos. 5,197,627; 5,346,093; and 5,381,923.
A principal deficiency of above-grade storage tanks is that the primary tank is exposed to physical dangers that can effect the life of the container. Surface mount tanks are particularly subject to i) potential cracking of concrete portions with thermal expansion and contraction; ii) rust or corrosion of metal components; iii) potential corrosion of reinforcement members within concrete portions; and iv) physical damage due to handling or collision from automobiles, trucks, on-site equipment or the like. Damage to any one of the container components can require replacement of the entire assembly.
Below-grade vaults can also suffer from problems of corrosion or cracking. Available double walled tanks, however, do not permit internal inspection or maintenance. The vault interiors are instead monitored with monitoring equipment of various types.
The below-grade containment vaults of the invention were developed to accommodate all enacted regulations, especially applications requiring storage of gasoline and petrochemicals. Another purpose was to accommodate user concerns to cost and repair or replacement of portions of the vault. Another was to provide a vault that is useable at fuel dispensing stations and depots. The vaults also include covered manholes and internal free space adjacent the primary tank(s) to facilitate internal inspection and maintenance.
One version of the vault is constructed in the form of a pre-cast concrete housing that contains one or more internal storage tanks. A base and cover are constructed to accommodate burial and support one or more liquid dispensers on the cover. A modular construction permits selective replacement of container components. A modular, construction also accommodates conventional pre-cast manufacturing processes and transport of the relatively heavy vault components.
Another double walled vault is constructed from steel. The steel vault is constructed to accommodate the same accessories. The primary tank(s) mounted within the vault can be constructed from steel, fiberglass or other appropriate materials. Manhole access and spill and rupture containment provisions are also provided at each vault.